1. Field of the Invention
The present invention relates to the technical field of cryptography and, in particular, the present invention relates to the technical sub-field of the cryptographic protection of a data exchange of two semiconductor chips.
2. Description of Related Art
Due to the clear increase in complexity in modern algorithms or circuits, the area available on a single semiconductor chip frequently is no longer sufficient to guarantee a compact integrated circuit and thus, by a small line length in this circuit, fast processing of such complex algorithms on the individual semiconductor chip is difficult to achieve. In order to counter this problem, two chips are frequently connected to each other in the prior art, as is exemplarily illustrated in FIG. 2. For this, an upper chip 200 is exemplarily connected to a lower chip 202 such that a first pad 204 of the upper chip is opposite a second pad 206 of the lower chip 202 and thus a contacting from the upper chip 200 to the lower chip 202 via corresponding contact points 208 is possible. However, such a partitioning of the processing of an algorithm or partitioning of a corresponding safety controller into two chips entails, additional safety risks and requires safety measures against new attack scenarios. When these two chips are connected to each other in the so-called face-to-face technology (F2F technology) and when it can be assumed that it is technically only possible entailing extreme efforts to separate the two chips from each other without destroying at least one of the chips, simple safety measures are possible to prevent spying out data from the one chip still functioning. Simple safety measures of this kind against spying out data of a chip still functioning are known to a person skilled in the art. Recent findings, however, have revealed that the chips may really be separated entailing reasonable efforts, such as, for example, by means of selective etching so that both chips on their own are still functioning. A potential attacker thus has the possibility to re-connect the two chips again by lines and, with regard to the communication between the two chips (such as, for example, between the upper chips 200 and the lower chip 202) via the contact points 208, to                a) intercept and        b) manipulate the communication (such as, for example, by a “man-in-the-middle” attack).        